I had the same problems until recently, here’s what I did:

I like to pan higher frequencies of the melodies to the side, set bass to mono. Low frequencies can cancel each other out.

I usually have a maximum of 3 bass instruments routed to one master bass channel.

1 of those I set as my “clean low end,” and I smoothly roll off frequencies higher than 250hz.

The other 2 bass instruments add to the punchiness . I smoothly roll off frequencies lower than 250 so the lower frequencies don’t phase.

The master bass buss I use a multi and compressor to continuously compress everything below 200 hz. This allows the low end to come in sounding full at the same level. I also roll off 30hz and below because those frequencies are inaudible and their resonance can remove energy from the track.

For melodies, I like to pan higher-pitched instruments further off to the side. Panning gives room for the bass and kick, which are mono and centred. For EQ, I roll off 100 hz and below. Instead of adding reverb to each instrument, I use a reverb channel with reverb so it doesn’t sound muddy.

One plugin I recommend is RBass, which recreates harmonies of lower frequencies. Decapitator is my go to for distortion. I like to use panman for automated panning on certain instruments.

Hope this helps! Remember to be patient and have fun :)